This invention relates to an apparatus and method for deposition of thin films. In particular, the invention relates to an apparatus and method for deposition of multicomponent (e.g., three or more components) oxide thin films, such as superconducting oxide films.
Since the discovery, in 1986, of high temperature superconductors of the perovskite family, considerable effort has been directed to the development of methods of forming highly aligned thin films of these superconductors on substrates. As the technology develops from research to commercialization of systems incorporating high temperature superconductors, a need has arisen for deposition systems suitable for commercial-scale manufacture. Such systems should be suitable for large-area deposition and should produce uniform films, both on a single substrate and between substrates. The films produced should be smooth and highly oriented, with a high critical temperature, Tc, and high critical current density, jc.
One conventional method of forming superconducting films includes co-evaporation of metals, such as yttrium, barium, and copper, followed by oxidation of the deposited metals. This method can be termed xe2x80x9creactive co-evaporationxe2x80x9d. The composition of the vapor in the co-evaporation chamber can be monitored or controlled using quartz-crystal monitors and a feedback device. The substrates upon which the film is to be formed are held in a rotating carousel and spaced from thermal boats that contain the material to be deposited. The substrates rotate between a deposition zone where they are exposed to mixed oxide vapors and an oxidation zone where the film is oxidized to form a superconductive oxide. The vapor pressure in the oxidation and deposition zones may differ by several orders of magnitude with very low pressures in the deposition zone. Typically, a layer with less than one unit cell thickness is formed during each rotation. The rotation allows for fast mixing of species on an atomic scale to produce a desired compound.
This method has several disadvantages. First, the thermal boats for the different materials must be close together to obtain a homogenous vapor. This limits the size of the thermal boats. Second, because the quartz-crystal monitors are not species specific, it is necessary to isolate the vapors seen by each monitor. This requires that the monitoring be done in the vicinity of the boats, rather than near the substrate. Third, the method does not allow for rapid cooling or convenient loading and unloading of the substrates. This decreases system throughput.
Generally, the present invention relates to methods and devices for forming thin films on a substrate. One embodiment is an apparatus including a deposition/reaction vessel and a holder for holding at least one substrate. The deposition/reaction vessel has at least three zones, each zone being separated from adjacent zones by a wall. The zones include at least two deposition zones, where each deposition zone is configured and arranged to deposit a deposition material on the substrate(s), and at least one reaction zone for reacting the deposition material with a reactant. The apparatus is configured and arranged to rotate the substrate(s) sequentially through the plurality of zones to form a thin film on the substrate(s). In some embodiments of the apparatus, the deposition/reaction vessel includes the same number of deposition zones and reaction zones. This configuration can include alternating deposition and reaction zones. In some instances, the holder is configured and arranged to hold substrates of different lateral dimensions.
Another embodiment is a method of forming a thin film layer on a substrate. A substrate is disposed in a holder and the holder is disposed in a deposition/reaction vessel. The deposition/reaction vessel includes at least three zones, each zone being separated from adjacent zones by a wall. The zones comprise at least two deposition zones and at least one reaction zone. The substrate is rotated through the zones. A deposition material is deposited on the substrate in each deposition zone. The deposition material is reacted with a reactant in each reaction zone. In some embodiments, a different deposition material is deposited in each of the deposition zones.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.